When you use a mill and cut this surface the cutter corner will aways be cutting across the surface you are trying to use as a sealing surface. Any small scratch or cutter mark creates a potential ditch from the combustion area to the outside. I am not saying it can not be done I just believe that you have a larger window for successful sealing when you cut this surface with a lathe and the cutter marks are less likely to cross the sealing area.

Very good thread. Smart guys weighing in.

Why hasn't anyone used the term "fly-cut"?

Regards,

A fly cutter is in effect just a large diameter single point face mill designed primarily for cutting across flat surfaces. Because of the counterbore of the sealing surface of 911 heads it is no more suited for this application than a smaller end mill.

Tor,

I had the same problem a few years ago on my 3.2. I decided to have a groove cut into the tops of the cylinders like on the 3.0 engines and use a CE ring. It worked like a champ. Ted Robinson did this for me at German Precision. I suspect you could have it done at a machine shop if you can get the dimensions of the groove from an SC cylinder. The other thing you really should do is replace the lower studs with steel studs. This will help the clamping force and eliminate the chance of a broken head stud.

-Andy